In file storage systems, it is common to locate the files based on importance, where volumes are created on multiple storage systems and sometimes interconnected to form a file hierarchy. In some of these systems the files, or portions thereof, are replicated to increase availability.
In such hierarchies, many problems can arise. For example, adding new storage and/or processing capacity can entail the costly redesign of storage and data infrastructures. File virtualization is often limited to the volume level, or file-stubs are used and thus, seamless file-virtualization with varied granularity is not available. The use of distinct file servers and file meta-data servers often prevents direct connection by clients. Also, the use of direct mapping by meta-data servers does not lend itself to scalable operation. In short, the usual top-down designs do not provide a unified hierarchy that can be accessed in a consistent manner and cause churn to the storage infrastructure in a big way when the storage hiererchies have to be redesigned.